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Old 22-10-2007, 08:08   #1
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gel batteries

Does anyone has good info regarding how one knows when Gel type batteries should be changed? How to test them for future failure?

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Old 22-10-2007, 09:23   #2
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Can't help on your specific query, but a friend runs a major battery business - he told me he's moving away completely from gel batteries for marine applications (because of problems he was not specific about) and favours the latest advances in traditional deep cycle units. I'll keep an eye on this thread and perhaps channel back some advice from him . . .
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Old 22-10-2007, 09:39   #3
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gasmag,

Depends on the batteries themselves, and how they've been treated.

For a battery study I did last year, I got hold of 4 golf-cart sized gel batteries which were 10 years old and had been used aboard a sailboat for that time. The sailboat stayed at the dock during the week, and only did weekend jaunts. The batteries were left on charge most of the time.

All four tested pretty good. One of the four tested almost new, and is still testing just great. (Testing done with a pretty expensive piece of gear which measures internal resistance; also, of course, with digital voltmeter, and 20-hour load testing while plotting voltage decay).

So, with luck, I'd say gels can last a pretty long time on a boat if they're taken care of!

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Old 23-10-2007, 10:12   #4
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Simple way is to establish a base line, and then track.

Charge fully, apply a known load for a known time, like leave the lights on for 12 hours measure the voltage with lights on, then turn off lights and wait then remeasure voltage say 12 hours later without charging. Try to do at a constant temp say a warm day every spring?

Make sure that the drawdown test is less than 50% of the battery capacity, you will see drawdown voltage and the recovery voltage fall as the battery wears out.
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Old 08-11-2007, 22:20   #5
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The proper way to test Gel Cell batteries is to do a "Load Test" on them. Any automotive shop can do that for you. Basically, they put a load on them and time how long it takes the voltage to drop under various loads.

Be careful when using gell cells. If you charge them over 14.5V, you may overheat and melt the casing. Most alternators are set to max output of 14.8V. You will need to turn your regulator down to 14.5V.

Many boats have had bad experiences with melted batteries due to not knowing to turn the regulator down. Gells take a full charge in a relatively short time. It will only take an hour or two of running to damage a new battery. This is quite common.

Gels typically last longer because they never run dry and the plates are less apt to deteriorate.
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Old 08-11-2007, 22:31   #6
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Quote:
Many boats have had bad experiences with melted batteries due to not knowing to turn the regulator down.
That is true for all batteries. You need to adjust the charging profile based on battery type. No battery will be a good choice unless you do this. There is no one setting fits all. It's best to adjust the voltages on the regulator as most can be tuned. Over or under charging are both bad. Modern AGM bateries have all but replaced the old gel batteries, but old style flood battery regualtors will trash them both quickly. Make sure both the regualtor and shore power charger can be set to the proper battery type.
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Old 16-11-2007, 14:11   #7
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Is there a way to do a load test on a battery without removing it from the boat? What's involved in doing one?

Thanks.

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Old 16-11-2007, 14:16   #8
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The automotive tester allows a short high amp current to flow that mimics a car starter. It then measures the batteries recovery.

If the voltage falls below I think 9.5 volts during dischage, or fails to recover its steady state voltage quickly, then it is kaput.

See above for the an easier way in the boat house batteries.
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Old 16-11-2007, 14:17   #9
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Is there a way to do a load test on a battery without removing it from the boat? What's involved in doing one?

Thanks.

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Old 16-11-2007, 16:20   #10
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